It looks like this might be a more appropriate forum than the single player one, so I'm moving the topic here (and modifying the subject a bit).

Old classic = I'm basically defining this as any campaign released before The Lost Levels (but excluding Bahagad Outbreak since it's by the same author). But I (hopefully) covered all the really well-known ones in the poll options. Which ones do you still enjoy, the ones you feel still hold up best? You can pick unlimited options here, but please only pick ones you legitimately still enjoy.

I had to group a few similar ones together to not run out of options. And I know I left out 'Chasm', but it seemed the most logical one to omit to fit the others in.

I'm not really sure how to vote on this one. I've played almost all of them in co-op over the last couple years in various (Rangers) Co-op Saturday events - with the notable exception of Ironstar and Ironblade due to reported issues that appear to make them non-viable in co-op - and can say I enjoyed all of them.

To different degrees, yes. Some are better than others - but they are all worth playing, if you have the time to play them all. Maybe some are more enticing to go back to, but recency (or more specifically lack thereof) is more of a determinant of that to me than quality, unless the mission is actually bad - and none of the above are.

Umm... it was either no/insufficient co-op player starts (a very common mistake) or that there was a crash somewhere. Might have been a crash - I forget. I got that info from a report from Whoskyd rather than first-hand - I haven't played them myself.

Edit: Looked it up. Ironblade apparently has only one start position, while Ironstar: "Crashed in a previous attempt, but this might not occur consistently"